A treatment that helps the human body fight blood cancer is showing early signs of promise against some solid tumors.

　　The treatment strengthens the person's natural defenses against disease. Its success against tumors suggests this method might be extended to more common cancers in the future.

　　The treatment is called CAR-T therapy. It involves making genetic changes to some of a patient's own cells to help them recognize and attack cancer.

　　Richard Carlstrand of Long Key, Florida, had the therapy more than a year ago for mesothelioma, a cancer of the lining of the lungs.

　　"We were going into unknown territories" to try this, he told The Associated Press. But now he shows no sign of cancer and "I couldn't be happier," Carlstrand said.

　　Experts discussed results of his and other cases at an American Association for Cancer Research conference last month in Atlanta, Georgia.

　　The United States Food and Drug Administration approved the first two CAR-T therapies in 2017 for some forms of leukemia and lymphomas. Leukemia affects the blood and bone marrow. Lymphoma is cancer that starts in infection-fighting cells of the body's immune system.

　　Researchers begin the treatment by altering immune system cells in a laboratory. They return the cells to the patient through an intravenous drip. This puts the cells right where the cancer is — in the blood.

　　But that method does not work well if the cells have to travel far through the bloodstream to get to tumors in the lung, breast or other places.

　　Prasad Adusumilli is a doctor with the Memorial Sloan Kettering Cancer Center in New York City. He notes that in those cases not enough of the cells may make it into the cancer to have an effect.

　　"Solid tumors are notorious for not letting the immune cells enter," Adusumilli said.

　　A bigger worry is that the proteins on solid tumor cells that these therapies target are also found on normal cells at lower levels. So the treatment also might harm them.

　　Adusumilli helped design a new CAR-T therapy to try to avoid these problems and tested it on 19 patients with mesothelioma. He also tested it on one patient with lung cancer and another with breast cancer. In these patients, the cancer had spread to the lining of their upper body. About 150,000 patients in the United States face this situation every year.

　　The altered cells were injected directly into the upper body where the tumors were. A genetic safety control was added so medicine could be given to destroy the cells if they caused harm.

　　After the therapy, doctors were able to perform a medical operation on the patient, who also was given radiation treatments. Twenty months later that person is doing well, with no other treatments planned. Fifteen other patients were well enough to start on a drug that improves the immune system in a different way.

　　Eleven of the 15 have been studied long enough to report results. Two had signs of cancer disappear for about a year, although one had the cancer return later. Six saw their tumors shrink. In three others, the cancer worsened.

　　There were no severe side effects; however, some patients had temporarily low blood counts and reported feeling tired.

　　Money from the U.S. federal government and private groups paid for the work. A larger study is planned. The Sloan Kettering Cancer Center has given Atara Biotherapeutics permission to use the treatment. The center may get payments from the company, as may Adusumilli.

　　A second study tested a different CAR-T therapy in 10 children and adults. All 10 subjects had advanced sarcomas — cancers that first appear in soft tissues or bones. Unlike other CAR-Ts that are usually given just once, this one was given more than once. In fact, one patient received the treatment 15 times since there were signs it was helping.

　　Shoba Navai is a doctor with the Baylor College of Medicine in Houston, Texas. She said that in her study, researchers collected a large amount of the CAR-T cells from patients' blood and then froze them. They would then return the cells to the patients intravenously, as needed.

　　Two of the 10 patients had all signs of cancer disappear, one for 17 months and the other for nearly three years. The disease appeared to be under control in two other patients. The conditions of five others worsened.

　　Side effects were similar to the other study. The therapy seems safe "and we have early signs that this treatment approach may help," Navai said.

　　Several organizations and non-profit groups paid for the work.

　　"These studies are showing there may be a path forward in solid tumors" with CAR-T therapies, said Louis Weiner. He directs the Georgetown Lombardi Comprehensive Cancer Center and was one of the conference leaders. CAR-T may hold promise for some cancers of the stomach, breast, lung and other areas, he said.

　　However, cost is a big issue. Current CAR-T therapies cost around $400,000, but can be made for far less than that in research centers. Doctors say they hope the cost will come down as more treatments come on the market and find their way to wider use.

　　I'm ­Alice Bryant.

　　And I'm Pete Musto.

　　Marilynn Marchione reported this story for the Associated Press. Pete Musto adapted it for VOA Learning English. George Grow was the editor.

　　We want to hear from you. How effective do you think CAR-T will be in treating cancer in the future? Write to us in the Comments Section or on 51VOA.COM.